The present invention relates generally to heat flux measurements and, more particularly, to a method for measuring the heat flux and total power dissipation per unit area of an object cooled in a liquid helium bath.
Cryogenics is the science pertaining to the production and effects of very low temperatures and employs various refrigeration techniques. With a suitable refrigeration process and the Dewar method of vacuum insulation, adequate quantities of liquid helium in a static condition can be utilized for cooling electronic devices during operation, such as Josephson junction arrays. However, because the Dewar-type insulation chamber is sealed to the atmosphere and obviously operates at extremely low temperatures, it is difficult to determine the power dissipated per unit area by an object while the device is in operation within the chamber. The ultimate performance of many cryoelectronic devices, such as semi- or super-conducting junction arrays, critically depends on minimizing the total power dissipation of the device.
In another cryogenic application, an accurate determination of the total power dissipated from a radioisotope, for example, tritium, provides an accurate assay of the total radioactivity of the material contained within the vessel. Techniques such as argon vapor boil-off rate measurements from a liquid argon bath which surrounds the vessel are elaborate and costly. Although the spatial distribution of power dissipated per unit area by the heat-emitting object may be determined optically, this method requires optical access to the interior of the Dewar-type insulation chamber. This optical technique, moreover, provides only the spatial distribution of the areal power dissipation and the calibration of this optical information to actual quantitative measures of the power dissipation per unit area is difficult. Obviously, providing optical access and the associated hardware required to optically determine the amount of power dissipated per unit area by the heat-fluxing object greatly increases the cost and complexity of the insulation chamber.
Consequently, a need exists for a simplified and improved method for measuring the total heat flux of a heat-fluxing object operating within an appropriate insulation chamber such as a Dewar-type insulation chamber.
These and other advantages and attainments of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawing wherein there is shown and described an illustrative embodiment of the invention.